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      01-01-2008, 08:55 PM   #43

Drives: e46 M3
Join Date: Dec 2007
Location: Earth

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Originally Posted by swamp2 View Post
This is not entirely true. Sure torque is intricately linked to displacement but there is significant variation in specific torque (tq/l). Consider the E46 M3 vs E46 M3 CSL:.

…….hp/tq/redline/hp peak@/tq@peak hp
M3: 343/269/7900/7900/228

Although the S54 was fairly maxed out (highly stressed) at 106 hp/l and 83 ft lb/l the M boys still found room for improvement. Although the CSLs peak tq only increased by 1.5% its tq increase at peak hp went up by almost 5%. Note that the rpm at which the peak hp is obtained did not change! This was accomplished almost entirely through improvements to “breathing” (intake/exhaust). Which is more important during very spirited driving when the car will typically be above 5000 rpm? Since the S65 is “only” producing 105 hp/l and 74 ft lb/l, I suspect there is substantial room for more. I’d expect the CSL to have AT LEAST: 450 hp, 8500 rpm redline, 300 ft lb AND 270 ft lb at hp peak (vs. approx 258 ft lb at peak hp in the base S65).

A bit more on redline: The S65 is really quite oversquare compared to the undersquare S54. The bore to stroke ratios are 1.2 vs. 0.94. A B/S of about 2.0 allows F1 engines to get very close to 20,000 rpm. We have heard rumors of BMW S65 durability testing at 9-10k rpm. The piston accelerations of the S65 do not even match those of the S54 until 8700 rpm. Furthermore, the S65 has smaller and lighter pistons. Putting all of this together if BMW was happy with the stress and safety factors in the S54 connnecting rods/pistons/crankshaft/etc. at 7900 rpm they should be equally happy going to at least 8700 rpm in the S65.
I'm not sure...

360/343 x 228 = 239 so the T increased proportionally to the HP...not greater

the new V8 is 25% larger, yet has only 13% more T...this tells me they must have limited T in the mid-range (cams, timing, etc.), to make it flatter...which implies the hi/lo extremes are not 'fiddled' with...

especially since the mep of the engine should be higher (due to a higher compression ratio...

I think with some cams and flow improvements this engine will reveal pretty good HP/mid-range torque gains...